Method of etching printing plates



'Feb 16,- 1960 l.. w. 's-rANDLEYV ll'l'zTl-Ion oF ETCHING PRINTING'PLATESv4 l Fil-6d Jun'e 25,` 1956 meting young party reu in Our |117 out areas andisolatedlhighliglit dot areason its surface.

object ofthe present invention is tof provide a, method along the line 9`9` of Fig. i8. f Referring tothe drawings,

' agitata' ,y Mnrnon o F nrlcrnisc; PniNTlNG *PLAT-Es.A LloydV Standley, Southold, NgY., alssignorQtGltden I @Hangman Yaris Appnatimmnezs, 1956; serial No. 593,493,- 1,1 lichter-fsa `The-present invention relatesto rriethorl` of" etching Y oft-theeprintin'gtplate 10 and'l the. inked; areas;l represent ther printing ."s'lrfaces` of 'the plate whichiarei 'in relief andtheltinirikedareas. represent surfaces that havev been retc'hedf..y In! a :combination plate, the "etched ar'eas vary considerably in depth, haswill beexplained hereinafter, andgthe rpresent. invention is. particularly directed to lthe etching ofz'such a plate. withoutiresort to theA conventional harid-pow'derin'g or.'sir"xiilar i methods vo f "controlling lateral etching of vertical'sur'faces exposed during ythe etchingloperations.v .t y The plate-is made .from an.` acidsoluble metal'.

` Suitableinetals include magnesium or highmagnesium `printing plates vandY relates, more ilparticularly, tor 1an improved method of etclifig'f'a ornbination-printing plate Inadefrom an acid solblemetal. ,f

As defined herein, a combination; printing plate` one-which has half-tone`areas, line areas, highlight drop-y offetching lsuch a' printing plate'iwhich doesnotrequir'e manual application of` pr'otectii/e'materialsV to surfaces of the plate thatare exposed during they etching. A1- though'plates having certain typesnof areas, such as line. 'areas or half-tone areas, have-been. 'etchedV previously without the manuali application of protective. mate'rials,"it. has not been possible toeth` plates having a combination ofareas 'on its surface satisfactorily`r by su'chfa procedure on a commercial basisv prior, to the presentinyention. l i

Another object of the present invention `is to provide a methodx of etching a combination plate wherebyvfblankingfofwof the etchinginl certain areas andV shoulderonthesu'rface ofthe plate are prevented'.` f

A further' object ofthe present 'nvention is to provide.

an economical and fast method of"etching"cornbination printing platesrwhieh may beqarres. out@ a` com'-V niercial with consistent and reliablegresi'ilts.k

Other objects and advantages of the inventioriwill.r b e plication andthe accompanying Fig. 1 is; a reproduction made from a` combination printing plate produced in accordance with the invention .ndis 'a plan view of the, surface offvfsucl'ray plate in reverse; f Y t Fig.r 2 .is a. fragmentary plan view illustrating aline area onthe surface of the` printing plate'vv shown inFig, 1 onan. enlarged scale;v

,l Fig. 3 isa section view, on anfe'nlarged scale, taken along the line. 3.,-f3fof: Fig. 2;, r A

Eig; 4 is. a fragmentary, plan view` il1ustrating;...a..half

tone area on the surface. ofthe, platefshowmixl Fig. ,l Y

on an' enlarged scale;

yapparentV and better understood;frornhe'followin apg "Fig, 5 ist-aV section view,-zon an enlarged scale, taken along the line'5.-5.'of.-Fig. 4;i t Y p.

. Fig. 6 isrraA fragmentarypla'n viewil1ustr atingA an iso lated dotarea yonv the surface; of therplate, shown` in, Fig. 1 onfan enlargedfscal;u Fig.- 7 `is az section view, onl along fthe. line 7:-7 oftFig. "6;

an. enlarged. scale,- talen Y"Fig Sfis afragmentary planvlew illustrating av highlightfdropoutlarea on the surfaeof; theplate shown in Fig. l on an enlarged scale;land1 Fig.' 9- is a section View, on. an enlarged;scaletaken f y Figgi yshow'sf.the etched surface olf-'ay combination printingA plate "10. which Vhas been' producedl in accordancewith the present; invention. t Fig, 1-'i`s"a reproduction-'made f'rorntheetched@ surface f and impurities,

To providedilerences halftoneyareas, thesize shape 'and spacingof'the print-l 'ingv surfaces mayf be varied. Such variations .are cornnionlyfdesignateddn terms, offlthe percent,v ofthe area v y', f foccupiedchytthezprintingsurfaces:and.rangefromma10% f y magnesiumbase'alloy is aniallloyhavingover percent magnsiumand anrexampleofffsuch au allo'yisione having" a nominal compositionofi percentaluminurn l Vperceiitzinc, and 0'.'2 '.pe`rcentr manganeisegwiththe balance vbeing magnesium. A 'high*zincbase4 alloy is on'ehaving"over.'90iprcent zinc'gaiidY an example ofI such an alloy is'one-co'mprising 9.9.2*.pe'rcent Zinc,v the balance being fpercenvtwPb 0.35.` percent` Cd, 0;()1 percentr Fe The, surface ofy thejplate; is prepared for etching in the usual manner by reproducing the image that is to bejprinted fon` the surface of the plate by well-known photographic processes. V'The'; photographic processing develops a resist on surface areas ofthe plate' that arel yto be in reliefv which/masks and protects such areas 'against the action of `vthreetc'zhingbaths to which the surface o f theplate is subjected. In the u nnliasltedV areas on the snnaceofy thejplate, the metal of. the plate is exposed andi's.subjecte'd to the etching.A actionV of -an'ac'id 'in' "anetching bath. This is av standard procedure'used 1in" the production fphotoengraved printing plates'which are commonly used? for the reproduction of advertising cuts-"or "similar illustration` in` newspapers or thel like- Printing. maybe done directlyV from the surface of such afplate'j or y'anmi'mpression of the surface of: the plate maybe 'madeby means Yof a mat for thepnrpose of casting'l'a` cylindricali printing plate for use ina rotary press. Thus," itis"importat'ftobefable to remove such'amat from the"'su`rfacefofwtheetched printing plate without daagc Yto tle'ma'tf` Y Asdefinedherein, a combination plate isa plate which hasa combinationlof line areas, half-tone areas, highlight dropoutfareas and i'soltedfdotareas etched'onfts sur'faclVTh'es areas' vdiffer in` their siiiface characf ferien/cs `andV in" the nepal" 'affetta requiret'ia arder far satisfactory'reproduction"of? the image to be made from ythe;plate?" For' 4illu',stra'tivfe purposes, examples olffthe reas'V on the surfaceI ofthe corribinaftionv plate various half-tone'arleais aline areais indicated @91.2% .shlisht'drowt are?, is indicated. at 13; "and an islateadotare@fisrinqieatea m14.'

A' 4'surface chara teristics ofv these, areas and the depths'jtowwhich are etched' are ,shown in enlarged jsoalsbythejllustrations ofFigsjZ through 9'. As shown v Y inflFig. 4, the surfaceof the half-tone area lll'jcon'si'sts of .$2,123.11 loqselyspaced relief ory printing surfaces 15vsepes or a the' p Sirfiacel ofthe.' 4i 1fr The Prinfig. Suffae are with i'esifstiny thephotographio process and i lose. spacing 'of theuprintingsurfaces, the the'spaceszlk lare etchedca'n be relatively depth to erallyI vbeing satisfactory;

shallow'with a depth offrfoin"k to ..006fof" inchjgenin the tone or ,shading in the t lamented instr,V 1s, v196e depressions ltwhich are etchedin illustrated in Fig. 4 is a 30% dot area.

dot area to a 90% dot area. The particular halftone area The size and shape of the etched spaces will also vary accordingly from about 0.015 of an inch for a dot area to about 0.001 of an inch for a 90% dot area. When `the area of the printing surfaces exceeds thearea of the* etched spaces, the etched spaces become dots and the printing surfaces occupy the remainder of the area.

As shown in Fig. 2, the line area @12 has solid or continuous printing surfaces 17fwhich are inl relief and are surrounded by open areas 18 etched inthe surface of the plate. As shown in Fig. 3, the open areas surrounding the line areas are etched to a depth of approximately .022 to .025 of an inch. An example of a line area is the typeformed on the surface of the plate. It will be noted that in certain letters, etched surfaces, as indicated at,18a, are surrounded by line;surfaces. etched area are small in size, they need not be etched to the full depth as the adjacent printing surfaces will prevent the inking rolls or the paper from contacting them in the printing operation.

As shown in Figs. 8 and 9, the highlight dropout area 13 is an open area etched in the surface of the plate. For satisfactory reproduction, such areas should be etched to a depth of approximately .022 to .025 of an inch. Highlight dropout areas are generally used to provide contrast or detail in the half-tone areas. As Will be seen from the surface of the plate 10, the highlight dropout areas vary widely in their dimensions and range in size from relatively small or narrow areas to large or open areas. small areas may be somewhat less than in the large open areas.

The highlight dot area 14, as shown in Fig. 6, consists of an isolated group of small closely spaced relief or printing surfaces 19 which are separated by etched spaces or depressions 20 which have been etched in the surface of the plate. The relief surfaces 19 and the etched spaces 20 correspond, in general, to the relief surfaces and the etched spaces in the half-tone area yand the spaces 20 are etched to approximately the same depth as the etched spaces in the half-tone areas. However, the isolated dot areas are entirely surrounded by an etched area, such as a highlight dropout area, which has been 'etched to a depth of approximately .022 to .025 of an inch.

During the etching of the plate, edges develop or form which define the printing surfaces which are in relief and it is of considerable importance that these edges slope outwardly at a slight angle as they extend downwardly in order for satisfactory reproductions to be made from the plate. An example of such an edge and the angle at which it slopes outwardly as it extends downwardly is indicated at 21 in Fig. 3. When this edge is undercut or yslopes inwardly, as indicated by the dotted line U in Fig. 3, the printing surface will be unsupported at its outer edges and may collapse or break away when rpressure is applied to it. Such undercuttng also makes it difficult to remove a printing mat satisfactorily from the surface of the plate. On the otherhand, Yif this edge slopes outwardly at too great anV angle, as indicated by the dotted line S in Fig. 3, it forms a shoulder adjacent the printing surface and poor denition of -the printed image will result.

It is also important that small or 'narrow highlight dropout areas and small openings in the line areas etch to their proper depth withoutblanking off orstopping of the etching in such areas. Otherwise poor definition and an unsatisfactory printing condition will result.

Hence, it will be seen from the foregoing that rather exacting standards must be met to produce a combination printing plate that will be satisfactory Afor printing purposes and because of differences in the character of the difficult to control the etching of combination plateswith the degree of certainty required for the production of such Y Where these Here again, the depth of etch required in plates on acommercial basis. However, the present discovery has eliminated these diiculties and makes it possible to etch combination plates with uniform and consistent results.

After the photographic processing of the surface of the plate referred to above has been completed, the plate is placed in an etching machine which contains a half-tone etching bath.

YIn general, an etching bath of the type disclosed in United States Letters Patent No. 2,640,765, issued June 2, 1952, to Easley et al., for Etching, may be` used in etching the plate and the etching may be carried out in a machine 'of the type disclosed in United States Letters Patent No. 2,699,048, issued February 16, 1954, to Easley et al., for Etching Machine. Reference may be made to such patents and the details thereof need not be described here.

Briey, the etching bath described in said Patent No. 2,640,765 comprises an aqueous solution which contains from 3 to 2O percent of HNO3 and has in admixture therewith an ester of sulfosuccinic acid and an aliphatic alcohol having from 4 to 12 carbon atoms Asuch as dioctyl sodium sulfosuccinate and a water-immiscible or.- ganic material such as the various petroleum fractions boiling in the range of to 390 C. of-which kerosene, benzine and the diethylbenzenes are examples. ;In general, the aqueous solution contains Vfrom 3 to 20 percent of HNO3 by weight with the amount of the wetting agent ranging from 0.003 to 0.04 times the weight of the HNO3 in the solution and the water-immiscible organic material ranging from 1 to 14 percent of the weight of the nitric acid solution. It will be understood that the present invention is not limited to the particular composition of the etching bath described in said patent and it is not limtied to the use of the machine described in Patent No. 2,699,048. Y

In order to etch the diiferent areas on the surface of a combination plate` to the depths required, the surface of the plate is contacted successively with two etching baths which are known as a half-tone bath and a line bath. In this procedure, a half-tone bath of the following composition may be employed: v

Half-tone etching bath (122 liters) The temperature of the bath is maintained at 72 F. and the plate is etched for approximately three'minutes and twenty-five seconds in this machine. During the etching, the paddles which impinge the bath against the surface of the plate of the machine are set at avspeed of about 500 r.p.m. for the rst 21/2 minutes and at a speed of about 350 r.p.m. for the remaining time.

As a result of the etching in the half-tone bath, the unprotected areas or spaces in the half-tone areas'are etched to approximately the required depth. Other uuprotected -areas on the vsurfacel of the plate vare also etched to this extent. However, if the etching inthe half-tone bath is continued beyondy this point, the edges of the more open areas which form during the etching will tend to become too sharp and to undercut. These open areas are the highlight dropout areas and the areas surrounding the line areas. In order to prevent this from occurring, further etching of the plate must be carried out by.a second etching bath which is slightly different in composition from the half-tone bath.

However, it has been found that when the plate is transferred from the half-tone bath to the second etching bath, it becomes di'icult to control further etching of the plate with any degree of certainty or uniformity. in the results obtained.V An explanation of this may .be

lthat vthe nitric -acid of the half-tone vbath reacts with ,lpliateandsgdium metasilicate. S w "able ohuneieially under th"tade'"name cgncefiitrrat'li'pn of the solution may 'I "aft "Rga'dlesf-s the'nature of rthis material or themanner ed, a residue or,r film from the 'haliwithout anlage to"th'e photographic resist if le gfherauiy deseableremaining-plate"with the alkaline solution first. l vi Suitable mail@A alliaiilianiatrialssfQr use ing soliitioi re trisdiuin"phosphtefbraig sodium silicates or cQmhinatiQnfthQRQ Sllil sflisodum v'rnfaterial is avail- The detergent used in the second solution should Abe of Athe'wetting agent type. 'Ihere are many suchdetergents available and examples'are detergents containing fatty alcohol sulfates, such as lauryl sulfate combined with polyphosphate or super-polyphosphates are suitable for this purpose. Othersuitable wetting agents include alkyl aryl sulfonates such as sodium isopropyl naphthalene anse and i the l phosy the etchedfsirfaceofthe plate asVK described above, the

' vr1the:s cople, of.: the1nvention as" defined by. the followingv ,.clainis.-4 Y f x etchedstotheir Proper 'Here' again the"concentration may ilary.1 widelyandya saturated r-nearlyfsaturated solution may be used-.

fAf-ter the-depositi or coating hasjbeen rer'novLedff-rom plate 'may then`V be rinsed V'aridi further etching offthe surface"oithe'y plate r'nay` b e c'arriedbut.` I ""'For"sch ffurtheret'ching,4 thefv plate is placed in, a sec'md etching machine of the same type, which contains a line etching bath. A specific example of a line .bath

'oi'suitable composition is as follows:l 'i

Line etching bath (izgvliia'rzslil i Diocityl sodiumsulfl succl Dissolved magnesium' leratu're of the, line bath is maintained at`72 g aiid` the platefis etched I for 'about e During'the',etchingithe 1sl regulated follows 30 seconds at 540` r.p.m. 4 5 seconds at'5l20-'r.p.m f 45 seconds atv l`500- r.p.m. 45-s`econds at 480 r.p.m.'y 44's`econ'ds at 46() r.p.ml Y40 seconds 'at.440y r.p.m. 40] seconds iat 420 r.p.m. 40 seconds aty 400 r.p.m.I Y 30 seconds at 380 r.p.m.l

A, It will beI noted that the secondi; etching bath includes ,akglautinsolution. The purpose of the gelatin solution -i sv;to` increase, the etchingI action ofthe bath yon flat surfacesA adjacent theetchdv-edgesof open4 areas vand in convtled-Y areas', which are protected to some extent from .direct'impingement of the bath thereonin the operation `iof v:the machine.

Under. the-.conditions Specified above, .the .Open vr-aras onthe surfaceof the plate, aswell, as confined areasaredepth* without blanking oiregardless offthesize of; theareas and; without undercutting or shouldering at the etched edges thereof. Such results may bereadily duplicated and satisfactorily etched platesl "may, thus,'be produced on a commercial basis. f. when the etchingofthe plate has been completed,A the etchedz` plateiis removed` rom the line machine and after being-rinsed, isready for use. 1 i ltavyillL bellnderstood that the specic compositions of thefetchingr baths Idescribedabove. are merelyy given as examples and the presenty invention is'notdirectedto the cmpositionof. these n :stood thatvarious modiicationsand changes may be made bathsr as` such. It will also befunderyinthegprocessv described herein without Ldeparting from v; 1'.: In.5agmethod; of. etching a. combination printing l'plategioffiani acid, soluble metal selected yfrom the' group consisting oif magnesium,A high magnesium-base alloys wherein the surface of the plate is contacted with two etching compositionsin separate steps, each Aof said etching compositionscomprising an aqueous solution of HNO3, said solution having in admixture therewith an ester of sulfosuccinic acid and an aliphatic alcohol hav-- ring fromv 4 to 12 carbon atoms and a water-immiscible sulfonate,rsodium butylbiphenyl sulfonate; dialkyl sulfosuccinates such as diamyl sodium sulfosuccinate wherein the alkyl group may have fromsix to eighteen carbony atoms. Such detergents are available commercially 'under the trade ALI-1s n petroleum fraction having an aliphatic side chain, thev `step'of removingfrom the surface of the plate the residue remaining thereon from the first of said two etchingV compositions by wetting the surface of the plate with an aqueous solution of a mild alkaline material selected 4 from kthe class consisting of trisodium phosphate, borax, Vsoclium'silicate, anda mixture of at least two of the liters '92.5.

foregoing materials, and thereafter scrubbing the surface of the plate with an aqueous solution containing aide- -tergent having wetting agent properties before contacting the Isurface of the plate with the second of said two etching compositions, said detergent being selected from the groups consisting of fatty alcohol sulfates, alkyl aryl sulfonates, and dialkyl sulfosuccinates, each alkyl group of said dialkyl sulfosuccinates having 6 to 18 carbon atoms.

2. The method of etching a combination printing plate as defined in claim 1 wherein the alkaline material is trisodium phosphate.

3. The method of etching a combination printing plate as defined in claim 1 wherein the alkaline material is trisodium phosphate and sodium metasilicate.`

4. In a method of etching a combination printing plate of an acid soluble metal selected from the group consisting of magnesium, high magnesium-base alloys, zinc and high zinc-base alloys wherein the surface of the plate is contacted with two etching compositions in separate steps, and the first of said etching compositions comprises an aqueous solution which contains from 3 to 20 percent of HNO3, said solution having in admixture therewith an ester of sulfosuccinic acid and an aliphatic alcohol having from 4 to 12 carbon atoms and a water-immiscible organic liquid selected from petroleum fractions having boiling points in the temperature range of 90 to 390 C., the step of removing `from etched surfaces of the plate the residue remaining thereon from the first of said etching compositions by wetting the surface of the plate selected from the class consisting of trisodium phosphate, borax, sodium silicate, and a mixture of at least two of the foregoing materials, and then scrubbing the surface of the plate with an aqueous solution containing a detergent having wetting agent properties before contacting the surface of the plate with the second etching composition, saiddetergent being selected from the groups consisting of fatty alcohol sulfates, alkyl aryl sulfonates,

and dialkyl sulfosuccinates, each alkyl group of said di' alkyl sulfosuccinates having 6 to 18 carbon atoms.

5. Ina method of etching a combination printing plate of an acid soluble metal such as magnesium or 'high magnesium-base alloys, said plate having portions of the'HNO3 in the solution and the waterimmiscibleorganic'liquid comprising from 1 to 14 percent of the weight of the aqueous nitric acid solution; then removing from the surface of the plate the residue of said etching composition by wetting the surface of the plate with `an aqueous solution of `a mild alkaline material selected from the class consisting of trisodium phosphate, borax, so-

dium silicate, and a mixturev of at least two of the foregoing materials, then scrubbing the surface of the plate 3.0 with an aqueous solution of a mild alkaline material with an aqueous-solution containing a; detergent. having wetting iagent prpertiesdsaid detergent being selected from the groups consisting of fatty,` alcohol sulfates, alkyl aryl sulfonate s,` and` dialkyl sulfosuccinates, each alkyl group of said `dialkyli sulfosuccinates. having 6 to 1 8 carf bon atoms, andthen impingingupon the surface of the plate a second etching composition. v Y

6. The method of etching a combinatonplate as de fined in claim 5 wherein the second etching composition includes the sameingredientsas-the first etching lcomposition. 7. The method of etching acombinationplateas defined in claim 5 wherein the water immiscible liquid is a petroleum fraction vhaving -aY boiling `temperature inthe range o f-90 to 390 C.

8. The method according to claim5 wherein the este;

is .dioctylsodiumsulfosuccinate andthe water immiscible liquid is diethylbenzene. v r

4.9. A method of etching a combination photoengraving plate; of acid soluble metalhaving halfftone and .line areas on its surface, ysaid surface being partiallymasked and havingfunmasked 4etchable areas onl its surfacewhich include confined areas in half-tone areas and op'en areas surrounding the line areas,whichv comprises etching the unmaskedI 'areas on the surface of said plate until ,a depth-of `approximately 0.005 of an inch is reachedin the half-tone areas by subjecting the unmasked areas to a' half-tone etching bath, said bath comprising an etching acid, a wetting agent and a petroleum fraction, said petroleum fraction adhering to and retarding action of the etching acid on exposed edges of the metal which are formed around the etched areas as the'etching progresses; then stopping the etching of theplate in the halftone bath vand removing from the etched areas on thesurfaceof theplate deposits formed thereon by the .action of the etching bath without removing the'masking from masked areas of the plate and then etching open areas ofthe plate to depths of at least .022 of an inch byisubjecting the surface of the plate to a line etching bath comprising an etching acid, a wetting agent and a petroleumfraction.' y

10. A method of etching a combination ,photoengraving plate as defined in claim 9 wherein theremoval of the deposits fromthe etched areas of the plate comprises applying an aqueous solution of a mild alkalinematerial to the surface of the platev and scrubbing the-.etched areas with said solution.

11. A method of etching a combination photoengrav ngplate as defined in claim9 wherein the removal of the deposits from the etched areas of the plate comprises t applying an aqueous solution of a mild alkaline material to the surface of the plate, scrubbing the etched: areas with said'solution and then washing the surface of vthe :platewith an aqueous solutionof a detergent having wetting properties.

References Cited in the file of this patent UNrTEDfsTATEs PATENTS y 1,709,327 "Spalding et al. Apr. 16, 1929 

1. IN A METHOD OF ETCHING A COMBINATION PRINTING PLATE OF AN ACID SOLUBLE METAL SELECTED FROM THE GROUP CONSISTING OF MAGNESIUM, HIGH MAGNESIUM-BASE ALLOYS WHEREIN THE SURFACE OF THE PLATE IS CONTACTED WITH TWO ETCHING COMPOSITIONS IN SEPARATE STEPS, EACH OF SAID ETCHING COMPOSITIONS COMPRISING AN AQUEOUS SOLUTION OF HNO3, SAID SOLUTION HAVING IN ADMIXTURE THEREWITH AN ESTER OF SULFOSUCCINIC ACID AND AN ALIPHATIC ALCOHOL HAVING FROM 4 TO 12 CARBON ATOMS AND A WATER-IMMISCIBLE PETROLEUM FRACTION HAVING AN ALIPHATIC SIDE CHAIN, THE STEP OF REMOVING FROM THE SULFACE OF THE PLATE THE RESIDUE REMAINING THEREON FROM THE FIRST OF SAID TWO ETCHING COMPOSITIONS BY WETTING THE SURFACE OF THE PLATE WITH AN AQUEOUS SOLUTION OF A MILD ALKALINE MATERIAL SELECTED FROM THE CLASS CONSISTING OF TRISODIUM PHOSPHATE, BORAX, SODIUM SILICATE, AND A MIXTURE OF AT LEAST TWO OF THE FOREGOING MATERIALS, AND THEREAFTER SCRUBBING THE SURFACE OF THE PLATE WITH AN AQUEOUS SOLUTION CONTAINING A DETERGENT HAVING WETTING AGENT PROPERITIES BEFORE CONTACTING THE SURFACE OF THE PLATE WITH THE SECOND OF SAID TWO ETCHING COMPOSITIONS, SAID DETERGENT BEING SELECTED FROM THE GROUPS CONSISTING OF FATTY ALCOHOL SULFATES, ALKYL ARYL SULFONATES, AND DIALKYL SULFOSUCCINATES, EACH ALKYL GROUP OF SAID DIALKYL SULFOSUCCINATES HAVING 6 TO 18 CARBON ATOMS. 